Support structure for z-extensible ct detectors and methods of making same

ABSTRACT

Pin-based support structures for easily and precisely assembling CT detector components into individual detector modules are described, as are methods of making the same. The pins in these structures serve as the local reference points against which all other detector components (i.e., collimators, scintillator packs, diodes, electronic flex connectors, etc.) are aligned. The pins may also be used to quickly and easily attach the individual detector modules to the local detector reference frame and then to the global reference frame in a CT imaging system. These structures allow CT detector components to be more easily and economically assembled than previously possible. Furthermore, these structures are extensible in the Z-direction, allowing for longer Z-coverage with each rotation of the gantry, thereby allowing for full organ imaging in a single CT scan.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation and claims priority of U.S.patent application Ser. No. 10/324,235 filed Dec. 19, 2002, thedisclosure of which is incorporated herein.

FIELD OF THE INVENTION

The present invention relates generally to a support structure andassembly method for Z-extensible computed tomography (CT) detectors.More specifically, the present invention relates to a pin-based supportstructure module, wherein the pins provide the reference points uponwhich all other components of a CT detector are aligned so as to allowfor easy and precise placement of all components thereof, and methods ofmaking same.

BACKGROUND OF THE INVENTION

CT imaging systems utilize a fan-shaped x-ray beam that is collimated tolie within the X-Y plane, or the imaging plane. The x-ray beam isattenuated by the object being imaged (i.e., the patient having the CTscan performed on them), and the x-ray is then detected by an array ofradiation detectors. Generally, this array of radiation detectorscomprises a plurality of individual detector modules, with each detectormodule forming a flat detector surface. The detector modules aregenerally positioned together in a side-by-side manner to form an arcthat is essentially centered on the x-ray source. In multi-slice imagingsystems, parallel rows of these detector modules may be arranged so thatdata corresponding to each single array row can be used to generate asingle thin slice image through a patient.

Behind the flat detector surface, each detector module comprises rowsand columns of detector elements aligned with X and Z coordinates,respectively. Additionally, each detector module generally comprisesdata acquisition circuitry that collects the x-ray intensity signalsthat are generated by the detector elements, and then converts theseintensity signals into CT numbers (i.e., Hounsfield units) which arestored for subsequent image reconstruction via back projection or thelike. Various other components, such as post-patient collimators,scintillator packs, photo diodes, and electronic flex connectors, mayalso be attached to these detector modules. All such attachments must beprecisely located with respect to one another, making the manufacture ofcurrent CT imaging systems very difficult. As such, extensive testing,reworking and realignment of the various components is often requiredbefore a CT imaging system of acceptable quality can be shipped to acustomer.

As there are presently no suitable systems and methods that allow CTdetector components to be easily and accurately assembled, it would bedesirable to have systems and methods in which such components could bemore easily assembled than currently possible. There is also a need forsuch systems and methods to allow such components to be precisely andaccurately assembled. There is also a need for such systems and methodsto utilize pins as reference points upon which all other detectorcomponents can be aligned. There is still a further need for suchsystems and methods to allow all the detector components to be assembledinto a single assembly module, which can then be easily positioned andaligned in the CT imaging system. There is yet a further need for suchsystems and methods to be less expensive than current assembly systemsand methods. Many other needs will also be met by this invention, aswill become more apparent throughout the remainder of the disclosurethat follows.

SUMMARY OF THE INVENTION

Accordingly, the above-identified shortcomings of existing systems andmethods are overcome by embodiments of the present invention, whichrelates to systems and methods that allow CT detector components to bemore easily assembled than currently possible, allowing the detectorcomponents to be precisely and accurately assembled into a module, whichcan then be easily positioned and aligned in a CT imaging system. Thesesystems and methods utilize pins as reference points upon which all theother detector components can be aligned. Many embodiments of thisinvention are less expensive than the current systems and methods forassembling CT detector components.

Embodiments of this invention comprise precisely-aligned CT detectormodules. These detector modules may comprise: a support structure; atleast one spacer; at least one alignment pin operatively coupled to theat least one spacer and the support structure to form a supportstructure sub-assembly; and a detector component operatively coupled tothe support structure sub-assembly, wherein the at least one alignmentpin is utilized as a local reference point against which the supportstructure, the at least one spacer, and the detector component areprecisely aligned.

Other embodiments of this invention comprise methods for easily andaccurately assembling a precisely-aligned CT detector module. Thesemethods may comprise: aligning a support structure, at least one spacer,and at least one alignment pin to one another; operatively coupling thesupport structure, the at least one spacer, and the at least onealignment pin to one another to form a support structure sub-assembly;aligning a detector component relative to the at least one alignmentpin; and operatively coupling the detector component to the supportstructure sub-assembly, wherein the at least one alignment pin isutilized as a local reference point against which the support structure,the at least one spacer, and the detector component are preciselyaligned. An assembly fixture may be utilized to align and assemble thedetector module. Embodiments may further comprise operatively coupling acollimator assembly to the detector module and/or operatively couplingthe detector module to the reference frame of the detector assembly andthe global reference frame of a CT imaging system.

Yet other embodiments of this invention comprise systems for easily andaccurately assembling a precisely-aligned detector module. These systemsmay comprise: a means for aligning a support structure, at least onespacer, and at least one alignment pin to one another; a means foroperatively coupling the support structure, the at least one spacer, andthe at least one alignment pin to one another to form a supportstructure sub-assembly; a means for aligning a detector componentrelative to the at least one alignment pin; and a means for operativelycoupling the detector component to the support structure sub-assembly,wherein the at least one alignment pin is utilized as a local referencepoint against which the support structure, the at least one spacer, andthe detector component are precisely aligned. An assembly fixture may beutilized to align and assemble the detector module. Systems may furthercomprise a means for operatively coupling a collimator assembly to thedetector module and/or a means for operatively coupling the detectormodule to a CT imaging system.

In many embodiments, the detector components may comprise, among otherthings, an electronic flex connector, at least one diode, and at leastone scintillator pack, wherein the electronic flex connector isoperatively coupled to the at least one diode and a data acquisitionsystem, and the at least one scintillator pack is operatively coupled tothe at least one diode. The detector module may also comprise acollimator assembly operatively coupled thereto. The electronic flexconnector, the at least one diode, the at least one scintillator pack,and/or the collimator assembly are preferably all precisely alignedrelative to the at least one alignment pin. These detector modules maybe operatively coupled to a CT imaging system, which is also preferablyprecisely aligned relative to the at least one alignment pin. A topsurface of the spacer and a bottom surface of the spacer preferably eachmeet a predetermined flatness requirement, and they also preferably meeta predetermined co-planarity requirement with respect to one another.The at least one alignment pin preferably meets a predetermined diameterrequirement, and when the at least one alignment pin is inserted into anaperture in the at least one spacer, the at least one alignment pinpreferably meets a predetermined perpendicularity requirement with thetop surface of the spacer and the bottom surface of the spacer.

Further features, aspects and advantages of the present invention willbe more readily apparent to those skilled in the art during the courseof the following description, wherein references are made to theaccompanying figures which illustrate some preferred forms of thepresent invention, and wherein like characters of reference designatelike parts throughout the drawings.

DESCRIPTION OF THE DRAWINGS

The systems and methods of the present invention are described hereinbelow with reference to various figures, in which:

FIG. 1 is perspective view of a CT imaging system;

FIG. 2 is a side view showing the basic components of a detector moduleutilized in embodiments of this invention;

FIG. 3 is a top view of a support structure utilized in embodiments ofthis invention; and

FIG. 4 is a top view of the spacers utilized in embodiments of thisinvention.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of promoting an understanding of the invention,reference will now be made to some preferred embodiments of the presentinvention as illustrated in FIGS. 1-4, and specific language used todescribe the same. The terminology used herein is for the purpose ofdescription, not limitation. Specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as abasis for the claims as a representative basis for teaching one skilledin the art to variously employ the present invention. Any modificationsor variations in the depicted support structures and methods of makingsame, and such further applications of the principles of the inventionas illustrated herein, as would normally occur to one skilled in theart, are considered to be within the spirit of this invention.

FIG. 1 shows an exemplary CT imaging system 10. Such systems generallycomprise a gantry 12, a gantry opening 48, and a table 46 upon which apatient 22 may lie. Gantry 12 comprises an x-ray source 14 that projectsa beam of x-rays 16 toward an array of detector elements 18. Generally,the array of detector elements 18 comprises a plurality of individualdetector elements that are arranged in a side-by-side manner in the formof an arc that is essentially centered on x-ray source 14. Inmulti-slice imaging systems, parallel rows of arrays of detectorelements 18 can be arranged so that each row of detectors can be used togenerate a single thin slice image through patient 22 in the X-Y plane.Each detector element in the array of detector elements 18 senses anddetects the x-rays 16 that pass through an object, such as patient 22.

Each row/array of detector elements 18 in this invention comprises aplurality of detector modules 50, wherein each detector module 50comprises all the relevant detector components (i.e., diodes,scintillator packs, collimators, etc.) in a single pre-assembledassembly, which may then be easily positioned within CT imaging system10. The present invention comprises systems and methods that allow theseCT radiation detector modules 50 to be very accurately and easilyassembled. These detector modules 50 comprise a support structure 52 andspacers 56 that allow all the detector components to be assembledtogether into a single assembly that can then be easily aligned andinserted into a CT imaging system 10. This invention utilizes pins 55 inthe spacers 56 (i.e., the pin/spacer assembly) as the reference pointsupon which all other detector module components (i.e., diodes,scintillator packs, collimators, etc.) are aligned, thereby allowing foreasy and precise placement of all detector components. This pin-basedsupport structure has many advantages: (1) the pins provide parallelsurfaces for mounting the detector module components upon; (2) the pinsallow the detector module to be precisely positioned and aligned in a CTimaging system; (3) the pins provide optical and mechanical referencefeatures for positioning the diode and scintillator pack(s) duringassembly of the detector modules; (4) the pins provide a precisemechanical location where a post-patient collimator may be attachedthereto; and (5) the pins allow the detector modules to be mechanicallyaligned and attached to the final CT imaging system (i.e., via elongatedslots in the support rails in some current CT imaging systems).

A side view of a detector module 50 as assembled in one embodiment ofthis invention is shown in FIG. 2. In this particular embodiment, thedetector module 50 comprises the following components: a supportstructure 52, an electronic flex connector 54, two pins 55, two spacers56, a diode 57, two scintillator packs 58, and a collimator assembly 59.

In embodiments, the support structure 52 for the detector modules 50 maybe made of any suitable high stiffness material, such as for example,compression molded carbon fiber. As shown in FIG. 3, the supportstructure 52 preferably comprises a rectangular shaped piece of materialhaving an elongated slot 61 in its central portion and apertures 60proximate each end. The final support structure also comprises twospacers 56, as shown in FIG. 4. Each spacer 56 may be made of anysuitable material, and preferably comprises an aperture 62 proximate oneend where a pin 55 may be inserted. The pins 55 on the spacer/pinassemblies provide the reference points against which all othercomponents of the detector module 50 will be aligned during assembly. Assuch, the top 70 and bottom 71 surfaces of each spacer 56 preferablyhave tight flatness and co-planarity requirements. Furthermore, the pins55 preferably have tight diameter requirements and, when pressed intothe spacers 56, have tight perpendicularity requirements with the top 70and bottom 71 surfaces of the spacers 56.

Preferably, the detector modules 50 are assembled in an assembly fixtureso that the detector components can be precisely and accuratelyassembled and attached to one another. For example, the pins 55 mayextend from the spacers 56 through the support structure 52 and intoprecisely located apertures in the assembly fixture.

In embodiments, support structure 52 may be inserted into the assemblyfixture. Next, the pins 55 may be inserted into the apertures 62 inspacers 56, which may comprise press-fitting the pins 55 into slightlysmaller apertures 62 in spacers 56. The spacer/pin assemblies may thenbe bonded or otherwise attached to support structure 52 in any suitablemanner. Once the spacers 56, pins 55 and support structure 52 areassembled, the free end of the electronic flex connector 54, whichpreferably has its other end bonded or otherwise attached to the backsurface of diode 57, may then be fed through the elongated slot 61 insupport structure 52. Diode 57 is the active portion of the detectormodule 50. The free end of electronic flex connector 54 carries theelectrical signals from the diode 57 to the read-out chips in a dataacquisition system in a manner well know in the industry. The diode 57(i.e., the back-bonded diode in this embodiment) may be aligned relativeto the assembly fixture and support structure 52 in any suitable manner,such as by optically or mechanically aligning features on the top of thediode 57 to the pins 55, and then the flex connector/diode assembly maybe attached to the support structure 52 in any suitable manner.Scintillator packs 58 may then be aligned relative to the assemblyfixture and support structure 52 in any suitable manner, such as byoptically or mechanically aligning features on the top of thescintillator packs 58 to the pins 55, and the scintillator packs 58 maythen be optically coupled to the diode 57 in any suitable manner, suchas by bonding or gluing. The scintillator packs 58 detect the x-rays,and then convert the x-rays into photons (i.e., visible light) that canbe detected by the diode 57. Thereafter, in embodiments, a collimatorassembly 59 that was specifically designed to align off pins 55 may bealigned with and operatively coupled to detector module 50 in anysuitable manner, such as by placing precisely-located apertures in thecollimator assembly over the pins 55. The collimator assembly 59 shapesthe detected x-rays to the focal spots of the detectors so as to reducethe scattered radiation caused by off-focal alignment. Gaps 51 may bepresent between the spacers 56 and the active portion of the detectormodule 50 (i.e., the active portion of the detector module comprises theelectronic flex connector 54, the diode 57 and the scintillator packs58).

The completed detector module assembly 50 preferably has pins 55protruding beyond the surface of the collimator assembly 59 so that thedetector module 50 can be assembled directly into the CT imaging system10, preferably via a precisely-located slot on the support rail(s) ofthe CT imaging system 10 into which pins 55 may be inserted. In thismanner, there should be no need to adjust alignment of the detectormodule 50 with the support rails, since the diameter of each pin 55 ispreferably only a few microns smaller than the slot(s) on the supportrails. While the other ends of pins 55 are shown extending beyond thesurface of the support structure 52, this may or may not be necessary,depending on the particular CT imaging system the detector module 50will be attached to.

As described above, the systems and methods of the present inventionallow the detector elements in CT imaging systems to be accurately andmore easily assembled than currently possible. Advantageously, themodular pin-based design of these support structures provides for thesimple alignment of all relevant components (i.e., diode, scintillatorpacks, collimator, etc.) to the same pin(s), which is utilized as alocal reference point for the entire detector module. Additionally, thisdesign is easily and continuously extensible in the Z-direction,allowing additional rows of detector modules to be added to lengthen thecoverage in the Z-direction. This invention allows each successive rowof detector modules to be positioned close enough to one another so thatgaps in Z-coverage are avoided. This is particularly advantageous sincethe medical industry now desires to have longer Z-coverage so that theycan get more coverage of a patient with each rotation of the gantry,thereby allowing full organ imaging in a single CT scan.

Various embodiments of the invention have been described in fulfillmentof the various needs that the invention meets. It should be recognizedthat these embodiments are merely illustrative of the principles ofvarious embodiments of the present invention. Numerous modifications andadaptations thereof will be apparent to those skilled in the art withoutdeparting from the spirit and scope of the present invention. Thus, itis intended that the present invention cover all suitable modificationsand variations as come within the scope of the appended claims and theirequivalents.

1. A CT detector module comprising: a support structure; a first and asecond spacer; a first alignment pin attached to the first spacer, thefirst alignment pin forming a first reference point; a second alignmentpin attached to the second spacer, the second alignment pin forming asecond reference point; and a plurality of detector components attachedto the support structure sub-assembly and aligned relative to each ofthe first and second alignment pins.
 2. The detector module of claim 1wherein the detector module is aligned to a CT imaging system via thefirst pin and the second pin, wherein the first pin and the second pinare positioned within alignment slots in a support rail of the CTimaging system.
 3. The detector module of claim 2 wherein a localreference frame is formed between the first reference point and thesecond reference point.
 4. The detector module of claim 1 wherein theplurality of detector components comprises an electronic flex connector,at least one diode, and at least one scintillator pack, wherein theelectronic flex connector is attached to the at least one diode and adata acquisition system, and the at least one scintillator pack isattached to the at least one diode.
 5. The detector module of claim 4wherein the at least one diode and the scintillator packs are alignedwith one of an optical and a mechanical alignment feature on the diodeand on the scintillators packs.
 6. The detector module of claim 4further comprising a collimator assembly attached thereto, thecollimator assembly having a first aperture and a second aperture, thecollimator assembly aligned relative to the local reference frame viathe first and second pins, wherein the first and second apertures in thecollimator assembly are positioned thereon.
 7. The detector module ofclaim 4 wherein the at least one diode is a back-bonded diode.
 8. Thedetector module of claim 1 wherein the first and second pins arepositioned in the first and second spacers, and the first and secondpins are aligned perpendicular to a top surface and a bottom surface ofthe first and second spacers.
 9. A method for assembling a CT detector,the method comprising: forming a local reference frame with at least twoalignment pins; aligning a support structure, at least two spacers, andthe at least two alignment pins to one another; operatively coupling thesupport structure, the at least two spacers, and the at least twoalignment pins to one another to form a support structure sub-assembly;aligning a plurality of detector components relative to the localreference frame; and operatively coupling the plurality of detectorcomponents to the support structure sub-assembly.
 10. The method ofclaim 9 further comprising aligning the plurality of detector componentswith an assembly fixture.
 11. The method of claim 10 further comprisingextending two alignment pins from the spacers, through the supportstructure, and into apertures in the assembly fixture.
 12. The method ofclaim 9 wherein the plurality of detector components comprises anelectronic flex connector, at least one diode, and at least onescintillator pack, and further comprising operatively coupling theelectronic flex connector to the at least one diode and a dataacquisition system, and operatively coupling the at least onescintillator pack to the at least one diode.
 13. The method of claim 12further comprising precisely aligning the electronic flex connector, theat least one diode, and the at least one scintillator pack to the twoalignment pins.
 14. The method of claim 9 further comprising aligning acollimator assembly to the plurality of detector components via the twoalignment pins and operatively coupling it thereto.
 15. The method ofclaim 9 further comprising aligning the plurality of detector componentsrelative to a CT imaging system via the two alignment pins andoperatively coupling it thereto.
 16. The method of claim 9 wherein uponinserting the two alignment pins into the at least two spacers, the twoalignment pins meet a predetermined perpendicularity requirement with atop surface of the spacer and a bottom surface of the spacer.
 17. Asystem for assembling a precisely-aligned detector module, the systemcomprising: a means for aligning a support structure, at least twospacers, and at least two alignment pins to one another; a means foroperatively coupling the support structure, the at least two spacers,and the at least two alignment pins to one another to form a supportstructure sub-assembly; a means for aligning a detector componentrelative to the at least two alignment pins; and a means for operativelycoupling the detector component to the support structure sub-assembly,wherein the at least two alignment pins are utilized as local referencepoints against which the support structure, the at least two spacers,and the detector component are precisely aligned.
 18. The system ofclaim 17 wherein an assembly fixture is utilized to align and assemblethe detector module.
 19. The system of claim 17 wherein the detectorcomponent comprises an electronic flex connector, at least one diode,and at least one scintillator pack, wherein the electronic flexconnector is operatively coupled to the at least one diode and a dataacquisition system, and the at least one scintillator pack isoperatively coupled to the at least one diode.
 20. The system of claim19 wherein the electronic flex connector, the at least one diode, andthe at least one scintillator pack are aligned relative to the at leasttwo alignment pins.
 21. The system of claim 17 further comprising ameans for aligning and operatively coupling a collimator assembly to thedetector module via the at least two alignment pins.
 22. The system ofclaim 17 further comprising a means for operatively coupling thedetector module to a CT imaging system via the at least two alignmentpins.
 23. The system of claim 17 wherein the at least two alignment pinsare positioned in the at least two spacers, and the at least twoalignment pins are aligned perpendicular to a top surface and a bottomsurface of the spacers.